1. Field of the Invention
The present invention relates to apparatus and methods using magnetoplastic and/or magnetoelastic materials for power generation. More specifically, the present invention relates to producing electrical current using magnetoelastic or magnetoplastic materials by “harvesting” or transducing energy from natural sources, especially from random, cyclic, and/or vibrational motion such as that produced by wind, waves, and human motion.
2. Related Art
Some magnetoplastic or magnetoelastic materials have been considered for use as actuators that convert electrical energy or changes in magnetic field to mechanical motion. Literature related to this topic is listed below:    Chernenko V A, Cesari E, Kokorin V V, Vitenko I N, Scripta Metal Mater 1995; 33:1239.    Chernenko V A, L'vov V A, Cesari E, J Magn Magn Mater 1999; 196-197:859.    Chernenko V A, L'vov V A, Pasquale M, Besseghini S, Sasso C, Polenur D A, Int J Appl Electromag Mech 2000; 12:3.    Chernenko V A, Müllner P, Wollgarten M, Pons J, Kostorz G, J de Phys IV, 2003; 112:951.    Ferreira P J, Vander Sande J B, Scripta Mater 1999; 41:117.    Jääskeläinen A, Ullakko K, Lindroos V K, J de Phys IV, 2003; 112:1005.    Murray S J, Marioni M, Allen S M, O'Handley R C, Lograsso T A, Appl Phys Lett 2000a; 77:886.    Murray S J, Marioni M, Kukla A M, Robinson J, O'Handley R C, Allen S M, J Appl Phys 2000b; 87:5774.    Müllner P, Int J Mater Res (Z f Metallk) 2006; 97:205.    Müllner P, Chernenko V A, Wollgarten M, Kostorz G, J Appl Phys 2002; 92:6708.    Müllner P, Chernenko V A, Kostorz G, J Magn Magn Mater 2003a; 267:325.    Müllner P, Chernenko V A, Kostorz G, Scripta Mater 2003b; 49:129.    Müllner P, Chernenko V A, Kostorz G, Mater Sci Eng A 2004; 387:965.    Müllner P, Ullakko K, Phys Stat Sol (b) 1998; 208:R1.    Pond R C, Celotto S, Intern Mater rev 2003; 48:225.    Sozinov A, Likhachev A A, Lanska N, Ullakko K, Appl Phys Lett 2002; 80:1746.    Straka L, Heczko O, Scripta Mater 2006; 54:1549.    Soursa I, Pagounis E, Ullakko K, Appl. Phys. Lett. 2004a; 23:4658.    Suorsa I, Tellinen J, Ullakko K, Pagounis E, J Appl Phys 2004b; 95:8054.    Tickle R, James R D, J Magn Magn Mater 1999; 195:627.    Ullakko K, J Mater Eng Perf, 1996; 5:405.    Ullakko K, Huang J K, Kantner C, O'Handley R C, Kokorin V V, J Appl Phys 1996; 69:1966.
Magnetoplastic materials, including ferromagnetic shape-memory alloys with twinned martensite, tend to deform upon the application of a magnetic field (Ullakko 1996, Murray et al. 2000, Chernenko et al. 2000). The magnetic-field-induced deformation can be irreversible (magnetoplasticity, Mullner et al. 2002, Mullner et al. 2003a) or reversible (magnetoelasticity, Chernenko et al. 2000, Ullakko et al. 1996). The magnetoplastic effect is related to the magnetic-field-induced displacement of twin boundaries, in an irreversible process. The magnetoelastic effect is also related to the magnetic-field-induced displacement of twin boundaries, but in a process that is at least somewhat reversible. While a strict definition of “elastic” would imply that magnetoelastic materials return without hysteresis to their initial state after removal of the magnetic-field, the term “magnetoelastic,” as it is frequently used, may include materials that deform and return to their initial state upon removal of the magnetic field either without hysteresis or with some hysteresis.
While literature on the subject of magnetoplasticity and magnetoelasticity has indicated such materials to be relevant as actuators for converting electrical energy, or changes in magnetic field, to mechanical motion, the invention utilizes the reverse effect for power generation, that is, the effect of strain-induced change of magnetization due to twin deformation/rearrangement.